1. Field of the Invention
The invention relates to a filter plate for a plate filter press including at least one press membrane covered by a filter cloth, wherein the filter plate and the press membrane have at least one common passage opening. The edge of the passage opening of the press membrane is provided with a continuous edge bead that is sealingly held in a groove along the edge of the passage opening of the filter plate by means of an annular fastening element.
2. Description of the Related Art
Such filter plates including a press membrane are known in principle in practice. A problem in connection with these plates is the connection between the press membrane and the plate body because during the pressing process a pressure medium is introduced between the plate body and the press membrane such that the press membrane is lifted away from the plate body. While the closing pressure also holds the press membrane itself against the filter plate in the edge region of the filter plate, the fixing in the region of the passage opening, particularly in the region of the slurry channel, poses a problem. In practice, the fastening in this region has in the past always been effected, for example, by simple gluing or vulcanizing of the edges of the press membrane to the plate body. However, gluing is not very reliable because extensive shear forces are generated during the pressing process which may cause the adhesive connection to come loose, particularly since, in contrast to fastening the membrane edges to the outer plate edge, the press membrane and the plate body are not supported by the press closing force in the region of the slurry entrance so that the adhesive connection in this region is subjected to great stress.
German Patent 2,324,876 discloses the provision of a continuous groove in the region of the filter plate center plane for the passage bore of the filter plate that is provided with press membranes. The edge bead of the press membrane is inserted into this continuous groove and a slotted spring ring is pushed over it. This spring ring is then held by engagement with a closed ring as the supporting ring. Such a fastening does not permit very high compressive forces. These can be realized, if instead of the supporting ring, a fastening is provided as it is known as a so-called cloth screw fastening. The screw-in flanges screwed against one another by a screwed-in threaded sleeve, which thus also clamp in the filter cloth, have been found acceptable in practice but have the drawback that filter presses equipped in this manner, can be used only within limits to process aggressive slurries. Charging the press membrane with a compressive pressure of up to 3 bar is possible. If higher pressures are employed there again exists the danger that the press membrane will be pulled out of its anchorage.